RGO/Manganese Silicate/MOF-derived carbon Double-Sandwich-Like structure as the cathode material for aqueous rechargeable Zn-ion batteries

Aqueous rechargeable Zn-ion batteries (ARZIBs) have been attracting a great deal of attention due to their immense potential in large-scale power grid applications. It is of great significance to explore cathode material with novel designed structure and first-class performances for ARZIBs. Herein, we successfully construct a double-sandwich-like structure, MOF-derived carbon/manganese silicate/reduced graphene oxide/manganese silicate/MOF-derived carbon (denoted as rGO/MnSi/MOF-C), as the cathode material for ARZIBs. Among the double-sandwich-like structure, manganese silicate (Mn2SiO4, denoted as MnSi) is in the middle of internal reduced graphene oxide (rGO) and external MOF-8 derived carbon (MOF-C). This integrated rGO/MnSi/MOF-C with double-sandwich-like structure can not only avert the sluggish electronic conduction progress caused by the conventional three-phase mixture system of rGO, MnSi and MOF-C, but also display promising Zn2+ storing capability. As expected, in mild aqueous 2 M (mol L-1) ZnSO4 + 0.2 M MnSO4 electrolyte, the initial discharge capacity of rGO/MnSi/MOF-C cathode reaches to 246 mAh·g-1, and the peak discharge capacity reaches to 462 mAh·g-1 at 0.1 A·g-1. This work not only involves the novel MnSi-based cathode for ARZIBs, but also first demonstrates our assumption of constructing the double-sandwich-like structure to improve Zn2+ storage. Moreover, the concept "double-sandwich-like structure" provides an idea for synthesizing the integrated carbon/transition metal silicates (TMSs)/carbon structure to boost the electrochemical properties of TMSs for energy-storing devices.